export const forEach = (arr, fn) => {
    if (!arr.length || !fn) return;
    let i = -1;
    let len = arr.length;
    while (++i < len) {
        let item = arr[i];
        fn(item, i, arr)
    }
};
export const uuid = (domain) => {
    let canvas = document.createElement('canvas');
    let ctx = canvas.getContext("2d");
    let txt = domain;
    ctx.textBaseline = "top";
    ctx.font = "14px 'Arial'";
    ctx.textBaseline = "tencent";
    ctx.fillStyle = "#f60";
    ctx.fillRect(125, 1, 62, 20);
    ctx.fillStyle = "#069";
    ctx.fillText(txt, 2, 15);
    ctx.fillStyle = "rgba(102, 204, 0, 0.7)";
    ctx.fillText(txt, 4, 17);

    let b64 = canvas.toDataURL().replace("data:image/png;base64,", "");
    let bin = atob(b64);
    return bin2hex(bin.slice(-16, -12));
};

export const bin2hex = (s) => {
    let i, l, o = '',
        n;
    s += '';
    for (i = 0, l = s.length; i < l; i++) {
        n = s.charCodeAt(i)
            .toString(16);
        o += n.length < 2 ? '0' + n : n;
    }
    return o;
};

export const encode = (str, pwd) => {
    let b = new Base64();
    pwd = uuid(pwd);
    str = b.encode(str);//Base64加密
    let prand = "";
    for(let i=0; i<pwd.length; i++) {
        prand += pwd.charCodeAt(i).toString();
    }
    let sPos = Math.floor(prand.length / 5);
    let mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5));
    let incr = Math.ceil(pwd.length / 2);
    let modu = Math.pow(2, 31) - 1;
    if(mult < 2) {
        alert("Please choose a more complex or longer password.");
        return null;
    }
    let salt = Math.round(Math.random() * 1000000000) % 100000000;
    prand += salt;
    while(prand.length > 10) {
        prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString();
    }
    prand = (mult * prand + incr) % modu;
    let enc_chr = "";
    let enc_str = "";
    for(let i=0; i<str.length; i++) {
        enc_chr = parseInt(str.charCodeAt(i) ^ Math.floor((prand / modu) * 255));
        if(enc_chr < 16) {
            enc_str += "0" + enc_chr.toString(16);
        } else enc_str += enc_chr.toString(16);
        prand = (mult * prand + incr) % modu;
    }
    salt = salt.toString(16);
    while(salt.length < 8)salt = "0" + salt;
    enc_str += salt;
    return enc_str;
};

export const decode = (str, pwd) => {
    if(!str){
        return null;
    }
    let b = new Base64();
    pwd = uuid(pwd);
    let prand = "";
    for(let i=0; i<pwd.length; i++) {
        prand += pwd.charCodeAt(i).toString();
    }
    let sPos = Math.floor(prand.length / 5);
    let mult = parseInt(prand.charAt(sPos) + prand.charAt(sPos*2) + prand.charAt(sPos*3) + prand.charAt(sPos*4) + prand.charAt(sPos*5));
    let incr = Math.round(pwd.length / 2);
    let modu = Math.pow(2, 31) - 1;
    let salt = parseInt(str.substring(str.length - 8, str.length), 16);
    str = str.substring(0, str.length - 8);
    prand += salt;
    while(prand.length > 10) {
        prand = (parseInt(prand.substring(0, 10)) + parseInt(prand.substring(10, prand.length))).toString();
    }
    prand = (mult * prand + incr) % modu;
    let enc_chr = "";
    let enc_str = "";
    for(let i=0; i<str.length; i+=2) {
        enc_chr = parseInt(parseInt(str.substring(i, i+2), 16) ^ Math.floor((prand / modu) * 255));
        enc_str += String.fromCharCode(enc_chr);
        prand = (mult * prand + incr) % modu;
    }
    //return enc_str;
    return b.decode(enc_str);
};

function Base64() {
    // private property
    let _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    // public method for encoding
    this.encode = function (input) {
        let output = "";
        let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        let i = 0;
        input = _utf8_encode(input);
        while (i < input.length) {
            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);
            enc1 = chr1 >> 2;
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            enc4 = chr3 & 63;
            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }
            output = output +
                _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
                _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
        }
        return output;
    };

    // public method for decoding
    this.decode = function (input) {
        let output = "";
        let chr1, chr2, chr3;
        let enc1, enc2, enc3, enc4;
        let i = 0;
        input = input.replace(/[^A-Za-z0-9+/=]/g, "");
        while (i < input.length) {
            enc1 = _keyStr.indexOf(input.charAt(i++));
            enc2 = _keyStr.indexOf(input.charAt(i++));
            enc3 = _keyStr.indexOf(input.charAt(i++));
            enc4 = _keyStr.indexOf(input.charAt(i++));
            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;
            output = output + String.fromCharCode(chr1);
            if (enc3 !== 64) {
                output = output + String.fromCharCode(chr2);
            }
            if (enc4 !== 64) {
                output = output + String.fromCharCode(chr3);
            }
        }
        output = _utf8_decode(output);
        return output;
    };

    // private method for UTF-8 encoding
    let _utf8_encode = function (string) {
        string = string.replace(/\r\n/g,"\n");
        let utftext = "";
        for (let n = 0; n < string.length; n++) {
            let c = string.charCodeAt(n);
            if (c < 128) {
                utftext += String.fromCharCode(c);
            } else if((c > 127) && (c < 2048)) {
                utftext += String.fromCharCode((c >> 6) | 192);
                utftext += String.fromCharCode((c & 63) | 128);
            } else {
                utftext += String.fromCharCode((c >> 12) | 224);
                utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                utftext += String.fromCharCode((c & 63) | 128);
            }

        }
        return utftext;
    };

    // private method for UTF-8 decoding
    let _utf8_decode = function (utftext) {
        let string = "";
        let i = 0;
        let c2,c3;
        let c = c2 = 0;
        while ( i < utftext.length ) {
            c = utftext.charCodeAt(i);
            if (c < 128) {
                string += String.fromCharCode(c);
                i++;
            } else if((c > 191) && (c < 224)) {
                c2 = utftext.charCodeAt(i+1);
                string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
                i += 2;
            } else {
                c2 = utftext.charCodeAt(i+1);
                c3 = utftext.charCodeAt(i+2);
                string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
                i += 3;
            }
        }
        return string;
    };
}